Complex dielectric permittivity and magnetic permeability of Fe/Fe ₃O₄ composite particles in 2-18 GHz

In the present study, iron/iron oxide (with a ratio of 4/1, 1/1, and 1/4) composite particles were prepared by precipitation. The morphology and phase composition were examined by scanning electron microscopy and X-ray diffraction techniques. The as-prepared composite particles were mixed with epoxy resin to prepare microwave absorbers and the corresponding electromagnetic properties were evaluated. The experimental results showed that the composite powder exhibited a mixture of α-Fe (∼4 μm) and Fe₃O₄ (∼30 nm) phases. The amount of iron oxide plays an important role in the electromagnetic properties of microwave absorbers. In general, complex permittivity (ε' and ε") and permeability (μ' and μ") increased with increasing amount of iron oxide additions. The minimum reflection loss can reach -16.7 dB at 9.0 GHz for 50 wt% of Fe/Fe₃O₄ = 1/4 composite absorber with 3 mm in thickness.